渤海湾盆地冀中坳陷古潜山的构造成因类型

冀中坳陷的潜山是油气勘探的重要领域。解剖潜山的地质结构、揭示潜山的成因机制是深化油气勘探领域的认识、深入分析潜山构造演化的关键。本文在覆盖全坳陷高精度的二维、三维地震资料,数百口深探井系统解释的基础上,应用构造解析方法,深入研究了潜山的地层系统、断裂构造与构造演化特征,提出了潜山成因分类的新方案。研究表明,冀中坳陷的潜山经历了前中生代建造形成、侏罗纪晚期挤压、白垩纪-古近纪多幕伸展断陷与新近纪-第四纪沉陷埋藏的形成过程;依据潜山发育的构造位置、构造变形特点与伸展变形的强度,将潜山划分为14种基本的成因类型;受控于长期演化及内外地质营力的联合作用,潜山多具有复合成因,在平面上不同成因类型的潜山带有规律地出现,主要有掀斜断块-高凸起型、反向断阶型、同向断阶-高凸起型、横向背斜或转换凸起-反转斜坡型、高凸起型-伸展外来断块型-反转斜坡型、高凸起型-双向旋转型-高凸起型、掀斜断块-变质核杂岩型等7种组合类型。其中,反向掀斜断块型、高凸起型、断阶型、反转型斜坡、外来断块型等成因类型的潜山因源-储组合、成山与成藏时期匹配而含油气性较好。冀中坳陷的潜山油气资源丰富,上述潜山成因分类方案有助于进一步剖析潜山的油气成藏机理与油气分布规律。

Structural genetic types of paleo-buried hill in Jizhong depression, Bohai Bay Basin

Buried-hill is an important exploration target in Jizhong depression. Analyzing its geologic structure and disclosing its formation mechanism is key to deepen the understanding of its tectonic evolution and the oil and gas exploration fairways. Based on the high-resolution 2-D and 3-D seismic data, and hundreds of deep exploratory wells across the depression, the paper used the structural analysis method to explore the buried-hill stratigraphic strata, fault system, and tectonic evolution as a whole, and put forward a new scheme for buried-hill genetic classification. It is shown that the buried-hill in Jizhong depression underwent a series of processes such as the sedimentary rock formation before Mesozoic, the compression in Late Jurassic, the multi-phase extension during Cretaceous to Paleogene, and the thermal subsiding and burying during Neogene to Quaternary. According to the tectonic location, the structural deformation feature, and the strength of extension, the buried-hill can be divided into 14 kinds of basic genetic mechanism. Due to the long period of tectonic evolution and the combined influences of the inner- and exo-genetic geological processes, the buried-hill has largely of a composite genetics. In map-view, the different genetic buried-hill zones exhibit regularly. It gives 7 kinds of structural association, such as, the tilted block and high bulge, antithetic fault step, synthetic fault step and high bulge, transverse anticline or relay high and inverted slope, high bulge and extension allochthon block and inverted slope, high high-bi-direction rotation-high bulge, tilted block and metamorphic core complex, etc. Among these, such types of buried-hills as the antithetic tilted block, the high bulge, the fault step, the inverted slope, and the allochthon block have favorable petroliferous potential owing to the matching of the source rocks and the reservoir rocks, the timing for trapping and accumulating. The oil and gas resource is much rich in Jizhong depression. The above genetic classification of buried-hill is helpful for addressing the oil and gas accumulation and distribution.